HIV virology and immunology Flashcards
Describe the trend in CD4 count as time passes with HIV
CD4 count denies rapidly in the first 6 weeks, then rises slightly up tot 12 weeks and then decreases again gradually over several years in a period of clinical latency, reaching almost 0 after 10 years
Describe the trend in HIV RNA copies in the plasma
Increases rapidly for 6 weeks and then decreases till 12 weeks and then slowly rises up till for the next several years until about 7 years when the RNA copies rises dramatically causing first constitutional symptoms and then opportunistic infections and then death
What is the period of time called in the first few weeks after infection when the CD 4 count drops dramatically and the number of HIV RNA copies in the plasma increases dramatically?
Acute HIV syndrome - wide dissemination of the virus occurs
What is the period of time called when the CD 4 count is low but rising over several years?
clinical latency - asymptomatic stage
When is HIV very contagious?
in the first month post-infection as there is high viraemia. The individual is still asymptomatic at this stage
Also contagious during the latent period usually about 7 years (not on treatment) as they continue to have sex
What type of virus is HIV?
enveloped retrovirus
What is a retrovirus?
A virus that contains reverse transcriptase, so can convert its RNA into DNA and incorporate it into the host DNA
What are the characteristics of lentiviruses?
slow viruses
long incubation period
To what genus do HIV1 and 2 belong
Lentivirus
How did HIV arise?
transmission of SIV (simian) from chimpanzees to humans
What are the three HIV types?
M - main
O - outlying
N - new
list the 6 steps of viral replication generally
- attachment
- cell entry
- interaction with host cells
- replication
- assembly
- release
What is the attachment step of HIV replication?
HIV gp120 binds to CD4 on host cells
Describe the cell entry aspect of HIV replication
only the central viral core carrying the nucleic acid and some associated proteins enters the host cell
Describe how HIV interacts with host cells
HIV uses cell materials (enzymes, a.a. and nucleotides) for their replication
HIV subverts host cell defence mechanisms
Describe the release of HIV from cells
exocytosis from the cell over a period of time
What is the most abundant type of WBC?
neutrophils
What do th1 cells do?
they produce specific interleukins (IL4,5,10,13) that cause maturation of B cells into plasma cells
What do th2 cells do?
Th2 produce INF alpha and TNF, which activate CD 8 cells turning them into cytotoxic T cells and NK cells, which produce perforin to cause lysis of infected cells
Which cytokine is important in the body’s response to TB?
INF alpha
What does CD 4 do in the normal immune response?
orchestrates the immune response: eosinophils, neutrophils, NK cells, macrophages, B cells, CD 8 cells
What is the problem with HIV activating CD 4 cells?
Activated CD 4 cells are destined to undergo activation induced cell death, leading to loss of CD 4 T cells
List the mechanisms with which HIV affects the immune system and leads to acquired immune deficiency
Activated CD 4 cells are destined to undergo activation induced cell death, leading to loss of CD 4 T cells
bystander cell death - infected macrophage causes death of infected VD 4 T cell
Thymus atrophy - preventing thyme maturation of T ce;;s
loss of bone marrow progenitors
fibrosis of lymph nodes
Describe the structure of HIV 1 **** listen to lec again
envelope gp 120 and gp 41 on surface of envelope matrix capsid containing p24 viral RNA and reverse transcriptase in core
